1. Field of the Invention
The present invention relates to composition of images acquired in time-series.
2. Description of the Related Art
In an imaging device such as a digital camera, a multi-exposure system for compositing continuously acquired still images to create one still image is known. Such composition of continuously acquired images enables obtaining one image having a trajectory of a moving subject shown therein. To obtain an excellent composite image, images to be composited must be positioned. For example, Jpn. Pat. Appln. KOKAI Publication No. 2010-252313 discloses a system for positioning images based on a global motion vector representing motions of entire images to eliminate an influence of camera shake of continuously acquired images and then compositing the images.
On the other hand, in general, when compositing images while positioning them, there is also a system for using a local motion vector that differs depending on each position in images to carry out positioning and composition, in place of obtaining one global motion vector with respect to the images. For example, Jpn. Pat. Appln. KOKAI Publication No. 2007-36741 discloses a system that can cope with a situation that subjects moving in multiple directions are present in images by increasing the number of target blocks for obtaining a motion vector. Further, Embodiment 1 of this publication discloses a system for detecting mobile objects or subjects, detecting a local motion vector in each region, and selecting an appropriate motion vector at each position in images from the motion vectors. Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 2010-1479.85 discloses a system for compositing images while performing positioning based on composition of local motion vectors and a global motion vector.